One of the representative methods for various color recording methods may be a recording method using an ink jet printer, that is, an ink jet recording method. This recording method involves producing small droplets of ink, and attaching these small droplets to various record-receiving materials (paper, film, clothes and the like) to perform recording. In this method, the method is characterized in that since the recording head and the record-receiving material are not brought into direct contact, the process is quiet with less noise generation, and size reduction or an increased speed can easily be achieved. Therefore, the method has rapidly become popular in recent years, and an extensive growth in use of the method is expected.
Conventionally, aqueous inks prepared by dissolving a water-soluble coloring matter in an aqueous medium have been used as the inks for fountain pens, felt pens and the like and as the inks for ink jet recording. In these aqueous inks, water-soluble organic solvents are generally added so as to prevent clogging of the inks at the pen tips or ink discharge nozzles. Furthermore, these inks are required to have advantages such as the production of recorded images of sufficient densities (high print density), no occurrence of clogging at the pent tips or nozzles, satisfactory drying properties on record-receiving materials, less bleeding, and excellent storage stability. Also, the water-soluble coloring matters used therein is required to have high solubility particularly in water, and high solubility in the water-soluble organic solvents that are added to the ink. In addition, the recorded images thus formed are required to have image fastness properties such as water resistance, light fastness, ozone fastness, and moisture resistance.
The above-described term ozone fastness is a resistance to the phenomenon that ozone gas present in air and having an oxidizing action acts on the coloring matter on a recording paper or within a recording paper and changes the color of an image recorded thereon. In addition to ozone gas, examples of oxidizing gases having this kind of action include NOx and SOx. However, among these oxidizing gases, ozone gas is considered as a main causative substance which accelerates the phenomenon of discoloration of ink jet recorded images.
Exclusive ink jet paper, which can give photographic image quality, is generally provided on the surface with an ink-receiving layer. In this ink-receiving layer, materials such as porous white inorganic substances are frequently used in order to reduce bleeding of the coloring matter for the purpose of speeding up drying of the ink and obtaining high image quality. In such an exclusive ink jet paper, significant discoloration of the recorded image due to ozone gas is observed. Since the phenomenon of discoloration due to an oxidizing gas, particularly ozone gas, is characteristic to ink jet recorded images, an enhancement of ozone fastness has been one of the most important problems to be solved in the ink jet recording method.
In order to expand the field of use of the ink jet recording method in those recording (printing) methods using ink in the future, it is strongly desired to further enhance various fastness properties such as light fastness, ozone fastness, moisture resistance and water resistance in the ink composition used in ink jet recording and the colored body colored by the ink composition.
Inks of various colors have been prepared from various coloring matters; however, while it is needless to say natural to use coloring matters having hues ranging from yellow to orange to brown to red, etc. for the expression of single colors, it is also one of the important coloring matters to be used to express different hues by being mixed with coloring matters of other colors, that is, to be used as coloring matters for color adjusting. For this reason, it is required to have high print density and to be excellent in various fastness properties, as well as to be excellent in the color fading balance between various hues such as yellow, magenta and black, etc. upon discoloration occurring at the time of exposure to light or the like. When coloring matters having poor color fading balance are used, only some specific hues are emphasized in a discolored recorded image, so that the color tone of the image as a whole is largely changed, and thereby the image quality is markedly impaired. Therefore, being excellent in this color fading balance is also one of the important performances of the coloring matter.
Patent Document 1 discloses a triazine dye that is incorporated into aqueous black ink compositions.
Furthermore, Patent Documents 2 and 3 disclose azo compounds having a hue ranging from yellow to red, or brown, and ink compositions containing these azo compounds.
Also, Patent Documents 4 and 5 disclose water-soluble azo compounds which are coloring matters of yellow color having crosslinking groups.
However, a coloring matter that satisfies the demands of the market has not yet been found.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2002-332426
Patent Document 2: WO 2006/001274
Patent Document 3: Japanese Unexamined Patent Application, Publication No. 2005-298636
Patent Document 4: WO 2008/142989
Patent Document 5: Japanese Unexamined Patent Application, Publication No. 2009-84345